Flat mop



FIG. 1 is a perspective view of a flat mop showing the new design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is an end view thereof;

FIG. 5 is another end view thereof; and,

FIG. 6 is a side view thereof.

The broken line showing of a mop handle is included for the purpose of illustrating environmental structure and forms no part of the claimed design. 

The ornamental design for a flat mop, as shown and described. 